The promotion of Mikhail Gorbachev to top job in the Kremlin a little over a year ago has commanded intense interest in the outside world. Two new biographies, one by a West German newspaper correspondent, the other by a Russian émigré, will in their different ways do something to satisfy that interest. But why exactly are we so interested?

Common-sense explanations start with the obvious fact of a generational shift in the Kremlin. For many years, the Soviet Union presented the image of a petrified gerontocracy where political leadership was the exclusive perquisite of the old and the dying. Leonid Brezhnev died on 10 November 1982; Yuri Andropov died on 9 February 1984; Konstantin Chernenko died on 10 March 1985; they were all of great age and feebleness, and they all gradually disappeared from view. The contrast between Mikhail Gorbachev, a man of vigorous middle age, and his three palsied predecessors, shuffling towards their catafalques, could scarcely be greater.

We are surprised by Mr Gorbachev’s modern walk-about style, by his relaxed professionalism in front of Western news reporters and television cameras, by the publicity given to his smartly-dressed wife, Raisa. We are fascinated by the speed and scale of his clear-out of the old generation of Brezhnev retainers (the term ‘purge’, with its Stalinist overtones, has been studiously avoided); by his crisp criticisms of corruption and bureaucratic incompetence; by the novelty of his crack-down on alcoholism; and by his overt espousal of economic reform. We are impressed by the apparent urgency with which he has pressed for better relations with the United States, and we are even a little taken aback by the radicalism and fertility of his public proposals for galvanising the arms-control process, moribund since 1979. Common sense tells us that this really looks like a man on the move, a man of dynamism, a man of the late 20th century, a man in charge, a man, above all, of change.

The very words betray themselves. At another level we are interested in Gorbachev because the Soviet Union is and has long been both threatening and baffling, and the more threatening because so baffling, so opaque, so apparently monolithic and rigid. Winston Churchill summed up our predicament in October 1939: ‘I cannot forecast to you the action of Russia. It is a riddle wrapped in a mystery inside an enigma.’ If we knew more about the policies and the policy debates of the Soviet Union, about the cabals and the springs of power, we might find it less threatening, or again we might not: but at least we should know more clearly where we stood and what challenges we faced. As it is, it is a matter of public notoriety that Western governments and the most expert advisers they can find are still not much past first base in trying to work out the irreducible objectives of the Kremlin. More than forty years have passed since the Second World War, yet Western governments still have difficulty in answering the most basic questions. Why is the Soviet Union so heavily armed? Is it because the Russian people, traumatised by centuries of foreign invasion, are obsessed by feelings of insecurity? Or because Communist ideology reinforces that other millennial tradition, of Muscovite expansionism?

Ideologues of left and right draw opposing conclusions from their own prejudices, but few serious analyses ever stray very far from the same well-worn banalities of speculative uncertainty. We do not know what the relationship is between the Soviet Union’s military capabilities and its political intentions; we do not know whether the détente of the early Seventies represented a genuine relaxation of attitudes on the part of a satisfied super-power which had achieved parity with its main rival, or a ploy to lull the West into a false sense of security. If it was the former, it is hard to make sense of the military build-up in the late Seventies, and the trouble-making in the Third World, culminating in the invasion of Afghanistan, which led to the election of Ronald Reagan. In short, we do not know very much of consequence – which is why the experts keep falling back on restatements of whatever happens to be the current cliché. An example is Paul Dibb’s The Soviet Union: The Incomplete Super-Power, whose thesis is that the USSR is strong in military terms, but weak in all the other ingredients of power – economic, technological, ideological. As far as it goes, the book is rather well done, but it does not tell us anything very illuminating and it doesn’t give us any guidance as to whether anything has changed, or is likely to change, as a result of Gorbachev’s accession.